The present invention relates to plastic fittings for joining sections of plastic tubing, and, more particularly, to plastic flare fittings.
Numerous industries use metallic tubes and fittings of copper, stainless steel, steel and various metal alloys where connection of high strength and integrity are needed. Metallic plumbing is very suitable in many applications. However, in certain industries, the fluids conveyed may attack metal components and the metal can contaminate the conveyed fluids, i.e., the semiconductor processing industry. Highly inert fluoropolymers may be utilized for the fittings, tubing, and components in such applications, for example, polytetrafluoroethylene (PTFE), and perfluoroalkoloxy (PFA). To maintain a clean and non-hazardous environment, it is essential that the fittings provided for coupling to sections of tubing are not easily unintentionally disconnected and that the tubing/fitting sealing interface maintains its integrity even under mechanical stress. Various types of fittings are known in the art for these purposes.
One common fitting formed from such polymers is the FLARETEK(copyright) fitting, available from Fluoroware, Inc., the owner of the instant application. Such fittings provide for a fitting body, with an elongate cylindrical nipple, a threaded portion at the base of the nipple and that completely covers the flared section of the tubing when attached and a fitting nut that is attachable thereto. A flared end portion of tubing is placed over the elongate tapered nose section with the fitting nut thereon. The fitting nut is then threadingly engaged with the fitting body compressing the flared end onto the nipple creating a seal between fitting nut, tubing and fitting body. In order to achieve this seal, the end of the tubing placed over the elongated tapered nose section is flared, prior to assembly, to the shape of the elongate nose tapered section. The flaring of the tubing is achieved by heating the tubing, then shaping the heated tubing into the desired flared configuration by pressing the heated tubing end over an appropriate form, such that the flared shape is retained by the end of the tubing.
This step of heating to a temperature sufficient such that the tubing may be permanently deformed and shaping the tubing prior to assembly with the fitting adds time and cost to the overall tubing/fitting assembly process. As such, there is a need for a fitting that is capable of flaring the tubing itself thereby eliminating the need for the heating and shaping of the tubing prior to assembly. The flaring of the tubing is preferably achieved by virtue of the assembly of fitting to tubing and, thus, there is a need that the fitting be readily graspable and, quickly and easily joined.
The needs described above are in large measure met by a self-flaring plastic fitting of the present invention. The self-flaring plastic fitting is utilized in coupling a tubing end portion to the fitting. The tubing end portion has a substantially uniform diameter and a groove about its periphery. The fitting itself includes a fitting body and a fitting nut. The fitting body is provided with a tapered nose section while the fitting nut is provided with a groove engaging device. In assembling the fitting, the end of the tubing incorporating the groove is inserted through the nut and is placed confronting the tapered nose section of the fitting body. The fitting nut is then pushed towards the fitting body where the groove engaging device of the fitting nut engages the groove of the tubing. The fitting nut threadingly engages with the fitting body and the fitting nut is drawn inwardly toward the fitting body and, correspondingly, the tubing is drawn against and over the tapered nose section of the fitting body causing the tubing to deform in a flare and a seal to be created between the tapered nose section and flared tubing.
The groove engaging device of the fitting nut may be unitary with the fitting nut or may be distinct therefrom. In the case of a unitary configuration, the groove engaging device preferably comprises an annular collar. In the case of a distinct configuration, the groove engaging device is preferably in the form of a retaining ring. Both fitting body and fitting nut are preferably provided with features for easier grasping and handling, e.g., fitting body is preferably provided with one or more planar surfaces for grasping with a tool while fitting nut is preferably provided with a plurality of winged extensions or knurled or ribbed surfaces for easier grasping and hand assembly. The tapered nose section of fitting the body is preferably of a shortened configuration requiring a minimal flare in the tubing. And, the fitting nut is preferably provided with an intermediate collar with a pinching extension that helps to pinch the formed flare of the tubing against the tapered nose section of the fitting body.
The fitting may be part of device or component or may have connection means such as external threads, another self-flaring fitting, or a flange.
When used herein xe2x80x9ctubingxe2x80x9d refers to a section of tubing or a tubular end portion where the tubular end portion is part of a device or component such as a valve or other fitting. Tubing formed of PFA is highly suitable for the self-flaring applications herein. xe2x80x9cPortionxe2x80x9d when used herein refers to either an integral or distinct and separable member.